METHODOLOGY FOR EARTHWORK IN EXCAVATION
(Acceptance Criteria: Ref. Section 300 of MORT&H)
This work shall consist of excavation by mechanical means in all types of strata, in rock by wedging/rock splitting or line drilling using pneumatic equipment and expanding agents, chiselling including dressing to final line, level, grades, cross-section as shown in drawings for roadway, drains, shoulders, median and foundation for structures, including hauling suitable excavated materials to site for embankment and sub-grade construction, also disposal of unsuitable cut materials in specified manner.
Procedure OF EARTHWORK IN EXCAVATION :
- The excavation shall be set out true to lines, curves, grades and sections as per drawings.
- In works involving widening of existing carriage way, shoulders, median shall be excavated to the full width and to the required levels as shown in drawings without disturbing the existing pavement. After reaching to the required depth up to 100-150mm after removing of all grass. roots stumps and deleterious material and compact it up to 90-95% compaction as per Lab MDD below the Embankment portion in case of OGL Stretch. And in case of above the OGL Level to the Subgrade top level we cane compact up to the 250mm compacted thickness in case of using 8-10 ton Vibratory Roller
- In works involving excavation for structures for construction of foundations for bridges, culverts, retaining walls, head walls, cut-off walls, etc. shall be excavated to required depth or level as shown in drawings. Where the nature of soil, depth of trench, season does not permits vertical sides, excavation shall be done with necessary shoring, strutting, planking or cut to slopes with safe angles with due regard to the safety of personnel and works.
- The cut formation, which serves as sub-grade has a density less than 17.5 Kn /Cum shall be loosened to a depth of 500 mm and compacted in layers and any unsuitable material encountered shall be removed and replaced with suitable material.
- While executing excavation all adequate precautions of soil erosion, water pollution shall be taken and appropriate drainage measures to keep the site free of water shall be taken. The suitable material obtained from excavation shall be used for filling of roadway embankment, filling of existing pits in the ROW, land scarping etc. All other unsuitable and surplus materials shall be disposed off from site and shall be stacked
- Rock when encountered shall be removed up to the required slopes, lines, depths Levels as prescribed in the drawings. Unsuitable shales and large boulders which cause differential settlements shall be removed to the extent of 500mm below the level prescribed in the drawings and shall brought up to the required cut formation with concrete of approved mix design or with suitable granular fill.
- All loose pieces of rock on excavated slope surfaces that move when pierced by a Crow bar shall be removed.
- In all cases at no point on cut formation the rock shall protrude above specified levels.